Field of the Invention
The present invention relates to a lens barrel provided in an image pickup apparatus such as a film camera or a digital camera, and an image pickup apparatus having the lens barrel.
Description of the Related Art
Some lens barrels provided in a digital camera or the like have a zoom mechanism that moves a plurality of lens holding frames, which respectively holds a plurality of lenses, in a direction of an optical axis through rotation of a cam cylinder while moving the lenses to predetermined positions by restricting rotation of the lens holding frames using a straight advance cylinder.
As the number of lenses has increased due to resent demand for an increase in shooting magnification, a whole length over which a lens barrel is extended tends to increase. It is thus important to secure strength of a lens barrel against external force such as drops. There has conventionally been proposed a technique that secures the strength of a lens barrel by providing a plurality of static pressure projecting portions in an outer peripheral portion of a straight advance cylinder inside the lens barrel (see Japanese Laid-Open Patent Publication (Kokai) No. 2013-156562).
However, according to Japanese Laid-Open Patent Publication (Kokai) No. 2013-156562 mentioned above, a second cam cylinder has a groove portion which is engaged with the static pressure projecting portions provided in the outer peripheral portion of the straight advance cylinder, and the second cam cylinder also has a straight advance groove formed at a deeper level than the groove portion so as to drive a first cam cylinder. Therefore, the second cam cylinder needs to have a thickness for accommodating the groove portion, which is to be engaged with the static pressure projecting portions, and a thickness for accommodating the straight advance groove for driving the first cam cylinder. This could hamper miniaturization of the lens barrel. Moreover, positional relationship between the static pressure projecting portions and the groove portion of the second cam cylinder varies with zoom positions, making it difficult to stably secure the strength of the lens barrel against external force.